Thanks for the update @developer6 
The link you shared is to the user migration (to Auth0) guide. Does that mean you’re migrating your users to Auth0? Rather that leaving users credentials in your custom (credential) store? For user migration to Auth0, the custom database login and get user scripts should suffice. Though if you want to support a user resetting their password as part of a login attempt, you will also likely need to implement change password too (see Change Password Script Templates for details). Until a user is migrated to Auth0, password reset will typically be performed against your custom (credential) store.
However if you are not performing user migration and you are also looking to support Signup via Auth0, you will typically need to implement a create script (see Create Script Templates for more details) as well. In this situation - i.e. where users are not being migrated - the same would go for change password too.
I’ve reviewed the logs again and now I see that not all users can login. There are lots of
Unexpected token < in JSON at position 0andUnknown clienterrors at login, sign up and password change events.
You might want to take a look at the troubleshooting section of the user migration guide here. This describes potential solutions for a number of situations, including the one it sounds like you’re currently experiencing (see here for details).
Hope this helps 